1. Field of the Invention
This invention relates to connectors for facilitating the mounting and demounting of earthmoving implements on and off an earthmoving prime mover such as a digger or front end loader. For the sake of simplicity, the term ‘digger’ will be used herein to refer to any such prime mover.
2. Description of the Related Art
In the absence of such a connector, an implement is usually mounted directly on the end of an arm assembly of the digger. Typically the implement is provided with a pair of spaced, mutually parallel mounting plates. The end of the arm assembly is received between the mounting plates. Two spaced, mutually parallel connecting pins pass through the mounting plates and the end of the arm assembly to join the two together. Under the action of a hydraulic ram arrangement mounted on the digger, the arm assembly is arranged to manipulate the implement. During such manipulation, the implement is able to pivot about the connecting pins.
It has been found useful to be able to mount a variety of implements on diggers and a great many connectors of the type envisaged herein have been proposed for the rapid changing of such implements.
3. Prior Art
Typically a connector comprises a body that is mounted on the end of the arm assembly of the digger. The body has a pair of side walls. Adjacent the connection with the arm assembly, the distance between the outer faces of the side walls is equal to the distance between the outer faces of mounting plates of an implement so that the end of the arm assembly can be received between the side walls of the connector in the same way as it is received between the mounting plates of the implement. Two connecting pins pass through the side walls and the end of the arm assembly to join the connector semi-permanently to the arm. In fact, the same connecting pins that, in the absence of the connector, are used to join the implement to the arm assembly are often used to join the connector to the arm assembly. Adjacent the connection with the implement the side walls of the connector are more closely spaced. In fact the width of the connector here is typically equal to the width of the end of the arm assembly so that this part of the connector is able to fit between the mounting plates of the implement. A second pair of connecting pins passes through the mounting plates and the side walls of the connector to join the implement to the connector. Again, the same connecting pins that, in the absence of the connector, are used to join the implement to the arm assembly are often used to join the connector to the implement.
The implement does not pivot relative to the connector once the two are joined together. Rather, the implement is fixed to the connector and the whole assembly (that is, the assembly comprising the connector and the implement) pivots about the first pair of connecting pins under the action of the aforementioned hydraulic ram arrangement.
In order to speed up the changing of implements, each implement is provided with its own pair of connecting pins for mounting the implement on the connector. These connecting pins are left in place semi-permanently on the implement. They are received in slots and/or catch arrangements provided at opposite ends of the connector. For example, the specification of British patent no 2205299 discloses a connector provided with slots at each end thereof. The slots are disposed at right angles to one another. By this means the connector, carried by the arm assembly of the digger, can be manipulated so that the slot at one end engages one of the connecting pins already mounted on the implement. The connector is then pivoted about that pin until the slot at the other end of the connector engages the second pin on the implement. A locking arrangement, typically controlled by a hydraulic ram, is then actuated to lock the second pin in its slot.
In another example, the specification of international patent application no. PCT/NZ00/00073 discloses a connector having only one true slot. As in the first example, the connector is manipulated so that the slot engages one of the connecting pins on the implement. The connector is then pivoted about that pin until the second connecting pin comes up against a land at the other end of the connector. A hook shaped plate mounted on the connector is actuated, again typically by a hydraulic ram, to hold the second pin in place against the land and thereby to lock the connector and the implement together.
It has already been mentioned that, in the zone adjacent the end of the arm assembly, the side walls of a connector are spaced further apart than they are in the zone adjacent the implement. For operational and safety reasons it is desirable, and even essential, that the implement should be mounted as close as possible to the end of the arm assembly. For these reasons each side wall is abruptly cranked inwards at the junction of the two zones. This causes design problems especially in the case of heavier connectors whose side walls are constructed of heavy steel plate. It is not generally feasible to bend such plate to achieve the degree of cranking required and the side walls of most connectors are consequently constructed of two overlapping steel plates welded together. The connectors disclosed in the two aforementioned patent specifications have such side walls.
Also, good design requires that reinforcing rings should be provided around the holes in the side walls that receive the connecting pins. Conventionally, such reinforcing rings are welded in place.
In addition, one of the aforementioned slots at the end of many conventional connectors is formed in the side walls and in a cross member that joins the side walls together. The cross member is typically formed from a length of heavy steel round bar that that is welded at each end to the side walls. The slot is cut by a machining operation after the parts are welded together.
All this has the result that the cost of conventional connectors so constructed is high on account of the cost of the labour required in the manufacturing processes.
As mentioned above, a mechanism operated by a hydraulic ram is often used to lock the connector and the implement together. The hydraulic ram is operated from the digger and considerably speeds up the changing of implements. In the course of use of such connectors it has nevertheless been found necessary to provide an additional safety device to lock the two together in the event that there is a failure of hydraulic pressure. One such arrangement is disclosed in the specification of New Zealand no. 250811. In this construction, the hook shaped members mentioned above that hold one of the connecting pins in the slot of the connector are carried on a sliding plate. One end of the sliding plate projects through an aperture in an end wall of the connector and the safety device takes the form of a safety pin that passes through the sliding plate and bears on the end wall. The safety pin prevents the sliding plate from sliding backwards and releasing the connecting pin from the slot. The safety pin is inserted by hand.
Similar arrangements involving the use of a safety pin have been devised for other known connectors. In all but one of such arrangements known to the applicant, the safety pin functions to lock the hook shaped member in place. The applicant is aware of one construction in which a safety pin functions to hold the connecting pin in the slot at the opposite end of the connector. In this case the connector in question is of the type having a cross member made up from round bar machined to form the slot as described above. When the connecting pin is in the slot the safety pin is inserted in registering holes predrilled in the round bar and the connecting pin. This arrangement has the disadvantage that the connecting pin must be turned so that the hole for the safety pin is lined up with the holes in the round bar and it is furthermore difficult to insert or remove the safety pin if it becomes bent in use.